Bill McKibbon, founder of 350.org, is predicting 20,000 demonstrators on the mall Sunday. Many are arriving from San Francisco, pressuring President Obama to nix the Keystone pipeline as comrade Garofoli has been documenting.

The fee-and-dividend idea is a clever twist on a carbon tax, putting a price on carbon at its source and rebating most of the money back to U.S. residents. Modeled on Alaska’s “permanent fund” that rebates oil royalties to Alaska residents, the idea has been promoted by McKibbon and NASA climate scientist James Hansen. The Boxer/Sanders bill is not quite so clean, as it uses a big chunk of money to invest in green technologies, but the idea is the same.

The fee-and-dividend idea offers a way around the political and distributional obstacles of a carbon tax. A price on carbon is widely considered essential to reducing greenhouse gas emissions, and is much simpler and more transparent than the cap-and-trade legislation Boxer sponsored in 2009. A carbon tax has potential appeal to conservatives, at least conservative economists, as a market based approach to reducing climate pollution, as well as to tax reform. A carbon tax is a consumption tax, which economists generally prefer to taxes on work, savings and investment.

Alex Bozmoski, director of strategy and operations for Inglis’s Energy & Enterprise Initiative, said it is “refreshing that Democrats are moving past cap-and-trade” but criticized the Boxer/Sanders bill as loaded with new renewable energy spending and “bloated government, and that is a fatal flaw for conservatives.” A better idea, he said, would be to offset the new revenue from the carbon fee with dollar-for-dollar cuts in other taxes and leave it to the market, incentivized by the carbon tax, to figure out how to cut emissions.

Sanders scored big by getting Boxer’s buy in. Boxer said she will push the bill through the Environment and Public Works Committee, which she chairs, holding hearings by spring and a markup in summer.

Boxer also said Republicans will not be able to stop the EPA from imposing new CO2 regulations on existing power plants because the Supreme Court has ruled that the agency must act on greenhouse gas emissions under the Clean Air Act.

Boxer cited climate scientists who briefed the committee Wednesday warning that major American cities such as San Francisco, New Orleans, Boston and Atlantic City will be under water this century if emissions continue on their current course. Among other things. Boxer called the situation a planetary emergency.